ZEKOO 7.5FT Rustic Double Style Sliding Barn Door Hardware Closet Roller Track Kit Main Material & Surfaceblack frosted, high quality carbon steel, corrosion protection, environmental protection, non-pollution. DesignTrack's hole: standard 16 inches. Track and roller arm thickness: 0.23 inches, very sturdy. Screws: 8.8 grade high strengh bearing capacity. Stopper: rubber covered, good buffer effect, reduce the noise. Roller bearingHigh purity bearing steel Gcr15, passed the test of opening - closing for 100000 times, wear-resisting, ensure the stability of the move and the wheel's fluency. productWe are professional factory, product has been tested and verified several times, accept custom-made barn door hardware. Our instruction are illustrated in inches, easy to install. Service5 years warranty, 100% money back guarantee, 24 hours online customer service, if any part missed or broken, we will ship out from U.S warehouse ASAP. Any problem in using it, our professional staff in the barn door hardware field will answer questions for you.